The early morning vote followed more than 10 hours of debate. The bill, which passed with a 20-16 vote, is supported by the Democratic governor and next goes to the House of Representatives, where it is expected to win approval.

The legislation won't affect sentences of the 11 inmates now on Connecticut's death row, including Joshua Komisarjevsky and Steven Hayes who were sentenced to death for a 2007 home invasion in Cheshire that left Jennifer Hawke-Petit and her two daughters, Hayley and Michaela, dead, and husband William Petit badly beaten.

Many officials insisted on that as a condition of their support for repeal. In fact, similar legislation which never made it to the Senate floor last year because of the on-going Petit trial.

Before the Senate voted, William Petit told reporters before a state Capitol news conference that he didn't think capital punishment would be abolished.

Connecticut has carried out just one execution in 51 years, when serial killer Michael Ross was administered lethal injection in 2005 after giving up his appeal rights.

In the past five years, New Mexico, Illinois, New York and New Jersey have all abolished the death penalty, and proposals are pending in several other states, including Kansas and Kentucky. California advocates have gathered enough signatures for an initiative to throw out the death penalty that is expected to go before voters in November.

Executions in the U.S. have declined from a high of 98 in 1999 to 43 last year, according to Richard Dieter, the executive director of the Death Penalty Information Center, a nonprofit capital punishment tracking organization in Washington, D.C.

"I think with the revelations of so many mistakes, aided by DNA testing, it's been made clear that the death penalty risks (innocent) lives," said Dieter.

"It moves us towards a more enlightened posture on the issue and puts us more in line with other New England states," he said.

A Democratic amendment to the bill, which also passed the Senate, would require that inmates convicted under the new law face harsh prison conditions replicating those on death row, including separate inmate housing, non-contact visitation and mandated cell movement every 90 days.